1. Field of the Invention
This invention relates to a light receiving circuit.
2. Background Art
In an optical coupler or an optical data link for transmitting digital signals, an optical digital signal is converted to an electrical digital signal by an optical receiving circuit. The optical receiving circuit includes photodiodes, transimpedance amplifiers, a differential amplifier, and a comparator. The output current of a photodiode that receives as input an optical signal is inputted to a transimpedance amplifier. The output current of a light-shielded dummy photodiode is inputted to a dummy transimpedance amplifier.
The output voltages of the two transimpedance amplifiers are inputted to the differential amplifier, which amplifies the difference of the output voltages and outputs a balanced signal and an inverted balanced signal. Furthermore, the comparator shapes the waveform. To enhance the signal transmission quality, it is necessary to reduce the pulse width distortion of the digital signal.
U.S. Pat. No. 6,885,249 discloses a technique concerning an optical signal receiving circuit that reduces pulse width distortion. In this technique, a level shift circuit is used to shift the voltage signal, thereby reducing pulse width distortion.